Liquid dispensers, such as liquid soap and sanitizer dispensers, provide a user with a predetermined amount of liquid upon the actuation of the dispenser. It is known to dispense liquids, such as soaps, sanitizers, cleansers and disinfectants from a dispenser housing that uses a removable and replaceable cartridge containing the liquid. In addition, it is sometimes desirable to dispense the liquids in the form of foam by, for example, interjecting air into the liquid to create a foamy mixture of liquid and air bubbles. Foam pumps typically include a liquid pump and an air pump, wherein the air pump is used to force air under pressure, and the liquid pump is used to pump the liquid under pressure into a mixing chamber where the air aerates the liquid thereby creating foam. Vortex foam pumps have been used in upright trigger sprayers; however, these vortex foam pumps are not suitable for use in an inverted position.